It is well known that various synthetic resinous materials are generally incompatible. Because of this, physical admixtures of most given different polymers such as those obtained from melt blending usually give opaque blended products. The theory and practice of polymer compatibility and blending is documented in "Polymer Blends", Vols. 1 and 2, by D. R. Paul and Seymour Newman, Academic Press Publishers of New York, San Francisco and London (1978).
There is an obvious need for desirable transparent polymer products for various applications including packaging purposes. Oftentimes there is need for better properties in materials desired to be utilized than are available in many of the known normally-transparent polymer products. Property modification is frequently desirable for many intended uses of transparent polymeric goods. Such properties as: improved heat deformation temperature characteristics better adhesion; improved light stability; and the like are advantageous.
It is frequently difficult to have all desired physical features in any single polymer material; such shortcomings of individual polymer species being commonly aggravated by the various requirements for polymer for various applications. Polymer blends are notoriously incompatible and not transparent in nature.
It is known that transparent polymer blends may be obtained if the refractive index of each of the component polymers are matched within about .+-.0.005 refractive index units. This is disclosed in U.S. Pat. No. 4,083,896. A similar result is often obtained when the component polymers are thermodynamically compatible. Polymethylmethacrylate and various styrene/acrylonitrile copolymers generally those containing between about 8 and about 28 percent by weight of copolymerized acrylonitrile have different refractive index values, form transparent polyblends; this presumably being due to the basic compatibility of the involved polymer species. French Pat. No. 1,526,375 is indicative of this.
Nothing in prior art reliably directs the successful realization of other advantageous transparent polyblends involving mixtures of polymethylmethacrylate and copolymeric styrene materials in order to get better and more satisfactory products therewith as in the present contribution to the art.